<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    while(true){
      let num = +prompt('请输入一个数字')
      if(num === 9){
          alert("猜对了")
          break
      }else if(num >9){
          alert("猜大了")
      }else if(num <9){
          alert("猜小了")
      }
    }
    
    // let num = +prompt('请输入一个数字')
    // console.log(num === 9);
  </script>
</body>
</html>